Enhancing carbon capture and lipid accumulation by genetic carbonic anhydrase in microalgae

Increasing atmospheric carbon dioxide (CO₂) has led to a series of problems, impacting both our lives and environment. One of the solutions to capture and reduce CO₂ is by carbon capture and storage (CCS). Carbonic anhydrase (CA) is an ancient enzyme existing in most organisms and it catalyzes the interconversion of CO₂ and bicarbonate (HCO₃ ⁻). Therefore, overexpression of CA in microalgae could be a potential way to capture excess CO₂ in an effective manner. In this study, an exogenous MlCA gene (i.e., 678 bp) which has been reported with highest catalytic activity was successfully overexpressed in Chlorella sorokiniana (CS) and Chlorella vulgaris (CV), respectively. The genetically engineered algae harboring exogenous CA were cultured in a specially designed Two-layer Photo Reactor (TPR) for validation. Transgenic algae with MlCA had improved biomass production, protein content and lipid accumulation. Finally, the transformants obtained a higher lipid amount up to 1.1 g/L which was 2.2-fold than that of wild types as well as accelerating the carbon capture and fixation.